1. Field of the Invention
This invention relates to a process of manufacturing track membranes by deep penetration of a working substance into and through the matrix of a polymer material. The working substance interacts with the matrix in the form of a high-speed jet generated and energized by an explosion of an explosive material.
2. Description of the Related Art
Membrane technology is a rapidly growing field with applications of great economical and ecological significance. Precision track membranes are well known in the art. A multitude of straight through apertures in sheets of various materials, such as polymeric plastic, formed by homogeneously bombarding the sheet of material with a source of heavy energetic charged particles (heavy ions) to produce damage tracks, have been described and claimed in U.S. Pat. No. 3,303,085 issued to Price et al. on Jan. 7, 1967, which is incorporated by reference herein. On subsequent stages of the membrane manufacturing process, the radiation damaged materials are removed by chemically etching the resulting membrane, for example by submersing the irradiated solid in an etchant. Various chemical reagents (etchants) and etching methods are described, for example, in U.S. Pat. No. 3,770,532 issued to Bean et al. on Nov. 6, 1973; U.S. Pat. No. 3,802,972 issued to Fleischer, et al. on Apr. 9, 1974; U.S. Pat. No. 7,001,501 issued to Spohr, et al. on Feb. 21, 2006; U.S. Pat. No. 7,597,815 issued to Desyatov, et al. on Oct. 6, 2009, which are all incorporated by reference herein. Membranes produced using the aforesaid methodology are usually characterized by average disperse dimension of open pores ranging from 10 nanometers to 10 microns. Needless to say, that the described method for manufacturing of membranes by means of heavy ion bombardment is very expensive and time consuming. On the other hand, there is a need in the industry for cheaper membrane products with dimension of open pores ranging from 1 to 500 microns.
At the same time, there are various methods of treatment of different materials and products, including polymers, with the use of explosive energy. For example, U.S. Pat. No. 4,960,430 issued on Oct. 2, 1990 to Koerber, et al. discloses a treatment of synthetic polymeric materials by contacting endless sheet-like, ribbon-shaped or filiform polymeric products with 0.1 to 2 mm size particles of sand, glass, corundum or a metal by directing onto the surface a stream of gas carrying the aforesaid particles. This gives the textile structures a rough, woolly, soft feel and they are mat, while films become rough and mat and have a low transparency.
A method of treating a surface of a polymeric article by impact implantation with particulate material to attain hardening, abrasion resistance or other altered surface characteristics is described in U.S. Pat. No. 5,330,790 issued to Calkins in 1994. High-pressure treatment with a slurry of a liquid mixed with a ceramic particulate material ranging in size from 66 to 350 μm, methods of ultrasonic and mechanical particle implantation are disclosed. Similarly, impact implantation with electrically conductive or magnetic materials can be employed to attain a conductive surface or a surface having electromagnetic radiation absorption characteristics. Along with other techniques said particulate material can be driven by shock waves created by detonation of a sheet explosive material. The invention may be practiced with the commercially available plastic materials, including the common thermoplastic such as the nylons, polyimides and polyetheretherketones, the polyolefins such as polyethylene and polypropylene, the fluoroplastics, polyamide-imides, polycarbonates, ABS, and others as well as thermoset plastics, and including filled, reinforced and composite variations of these materials. Ceramic macro particle for implantation was selected from the group consisting of electro-corundum (Al2O3), boron-carbide (BC), silicone-carbide (SiC), titanium diboride (TiB2), boron nitride (BN), quartz (SiO2), garnet, zirconium, or a mixture of the above.
Russian Pat. RU 2,425,912 issued to Ulyanitsky et al. in 2011 discloses a procedure for metallization of polymer materials by detonation sputtering. Preliminary modification of surface of polymer material is performed by acceleration of particles of metal with a shock wave formed before detonation front causing their penetration into surface of polymer material. A metal layer is applied on modified surface with flow of these particles accelerated with products of detonation of gas mixture.
As would be appreciated by persons of skill in the art, the explosive methods described above are surface treatment methods which are not suitable for producing track membranes. What is needed is a method for new material treatment involving deep penetration.
One method of deep penetration is described in detail by S. Usherenko in U.S. Pat. No. 7,897,204 issued on Mar. 1, 2011. It is a process of strengthening the matrix of a high-speed steel for forming a composite tool material by SDP (Super Deep Penetration) of reinforcing particles into and through the matrix of the tool material. The particles interact with the matrix in the form of a high-speed jet generated and energized by an explosion of an explosive material that contains the premixed powdered components of the working medium composed of particles of a hard material and ductile metal, and if necessary, with an addition of a process liquid. The particles of the working medium material have dimensions ranging from 1 to 100 μm. The jet has a pulsating nature with the velocity in the range of 200 to 6000 m/sec and a temperature in the range 100 to 2000 C. As a result of strengthening, the steel matrix is reinforced by elongated zones of the working material particles which are oriented in the direction of the jet and occupy less than 1 vol. % of the matrix material, while less than 10 vol. % is occupied by the zones of the matrix restructured as a result of interaction with the particles of the super-high velocity jet.
However, a demand exists for explosive material treatment methods that could be applicable for treating materials other than metals, e.g., for the preparation of polymeric membranes.